1. Field of the Invention
The present invention relates to a camera loadable with a photo film cassette. More particularly, the present invention relates to a camera with a photo film advancing mechanism having a small size and feeding and returning photo film of a photo film cassette.
2. Description Related to the Prior Art
The IX240 type of photo film cassette is known in the field of photosensitive material. The photo film cassette has photo film which is entirely contained in a cassette shell when unexposed. A spool in the photo film cassette is rotated in a photo film unwinding direction so as to advance a leader end of the photo film to the outside of the cassette shell. There are various types of cameras for use with the IX240 type. The cassette shell in the photo film cassette is formed from plastic material with lightshielding opacity.
JP-A 9-281574 (corresponding to U.S. Pat. No. 5,835,805) discloses an example of photo film advancing mechanism in the camera of a type for use with the IX240 type of the photo film cassette. The photo film advancing mechanism includes a spool drive shaft and take-up spool. The spool drive shaft is engageable with a spool in the photo film cassette. The take-up spool winds up the photo film fed from the photo film cassette. The spool drive shaft is rotatable in the photo film unwinding direction and a winding direction by changing over a motor between two rotational directions. Rotations in the photo film unwinding direction feed the photo film from the cassette shell. Rotations in the winding direction return the photo film into the cassette shell. The take-up spool rotates in a photo film take-up direction to wind the photo film.
A rotational speed of the take-up spool at its peripheral surface is predetermined higher than a rotational speed of the spool drive shaft in the unwinding direction so as to capture a leader end of the photo film reliably. When the leader end of the photo film is taken up by the take-up spool, accidental tension may be applied by the take-up spool to the photo film due to inequality in the rotational speed of the spool drive shaft and take-up spool. To prevent such an accident, a clutch mechanism is added to the photo film advancing mechanism for allowing the spool drive shaft to rotate freely upon pulling of the take-up spool for the photo film. Also, a sun and planet gear unit is incorporated for changing over transmission of motor rotation between the spool drive shaft and take-up spool at the time of photo film feeding and returning.
There are suggestions of reducing a size of the camera to make much use of the small size of the IX240 type of the photo film cassette that is smaller than 135 type. However, the photo film advancing mechanism of the prior art has the sun and planet gear unit and various transmission gears meshed with the sun and planet gear unit either of which includes numerous parts juxtaposed horizontally in a space inside a lower face of the camera. This conventional structure is inconsistent to reduction of the size of the camera.
If the camera has a small size, it is difficult or impossible to keep spaces at outer faces of the camera for lids, doors or portions of access to inner chambers in the camera. In the known type of the camera for use with the IX240 type of the photo film cassette, there is an unused space inside a lower face of the camera. It might be conceivable to dispose a battery chamber and battery chamber lid in such a space. However, there is no known construction enabling this construction, the camera accommodates a train of plural speed-reducing gears in the space inside the lower face for connection between the take-up spool and spool drive shaft.
In view of the foregoing problems, an object of the present invention is to provide a camera having a photo film advancing mechanism and in which spaces inside a camera body can be saved structurally.
In order to achieve the above and other objects and advantages of this invention, a camera is loadable with a photo film cassette including a cassette shell, a spool contained in the cassette shell in a rotatable manner, and a photo film wound about the spool in a roll form. In the camera, a cassette holder chamber contains the cassette shell. A roll chamber is provided, into which the photo film is advanced from the cassette shell. A spool drive shaft is disposed to project from an inside of the cassette holder chamber, connected with the spool coaxially, for rotating in an unwinding direction, to feed the photo film from the cassette shell, and for rotating in a winding direction, to wind the photo film back to the spool. A take-up spool is disposed to project from an inside of the roll chamber, for rotating in a take-up direction, to take up the photo film from the cassette shell. A motor makes a forward rotation to feed the photo film, and a backward rotation to return the photo film. A sun and planet gear mechanism includes a sun gear for rotating in a first direction in response to the motor forward rotation, and for rotating in a second direction in response to the motor backward rotation. A feeding planet gear and a returning planet gear are meshed with the sun gear. An arm supports and keeps the sun gear and the feeding and returning planet gears meshed with one another in a rotatable manner. A first feeding transmission gear is meshed with the feeding planet gear revolved about the sun gear, for rotating in the first direction in response to the motor forward rotation, to cause the spool drive shaft to rotate in the unwinding direction. A second feeding transmission gear is meshed with the feeding planet gear revolved about the sun gear, for rotating in the first direction in response to the motor forward rotation, to cause the take-up spool to rotate in the take-up direction. A returning transmission gear is meshed with the returning planet gear revolved about the sun gear, for rotating in the second direction in response to the motor backward rotation, to cause the spool drive shaft to rotate in the winding direction. The first and second feeding transmission gears and the returning transmission gear are disposed coaxially with one another.
Furthermore, a clutch mechanism selectively sets connected and disconnected states between the first feeding transmission gear and the spool drive shaft, and during an initial step in the motor forward rotation, the clutch mechanism setting the connected state, and after the initial step in the motor forward rotation, the spool drive shaft being rotated at a higher speed by feeding of the photo film, the clutch mechanism setting the disconnected state to free the spool drive shaft from the first feeding transmission gear.
The returning transmission gear is connected with the first feeding transmission gear by setting of the connected state in the clutch mechanism, rotated by the first feeding transmission gear, for rotating the spool drive shaft.
Furthermore, a timing belt is moved round by the returning transmission gear, for rotating the spool drive shaft. A camera incorporated part is disposed along the timing belt. At least one tension roller for flexing the timing belt to prevent interference with the camera incorporated part.
The camera incorporated part is a battery or an electronic flash main capacitor having a cylindrical shape and oriented to extend horizontally.
The clutch mechanism is disposed coaxially with the first and second feeding transmission gears and the returning transmission gear.
The clutch mechanism includes a first group of plural ratchet claws arranged in the first feeding transmission gear to project toward the returning transmission gear, each of the ratchet claws having a first erect face and a first inclined face. A second group of plural ratchet claws is arranged in the returning transmission gear to project toward the first feeding transmission gear, each of the ratchet claws having a second erect face and a second inclined face. The first and second erect faces become engaged with each other upon rotation of the first feeding transmission gear in the first direction, for rotating the returning transmission gear in the first direction, and the first and second inclined faces slip from each other, for allowing the returning transmission gear to rotate in the first direction relative to the first feeding transmission gear.
Furthermore, a coil spring pushes the first feeding transmission gear toward the returning transmission gear.
The timing belt is disposed under the roll chamber and the cassette holder chamber, and extends therebetween. The returning transmission gear is disposed under the roll chamber. Furthermore, a driven timing gear is disposed under the cassette holder chamber, meshed with the timing belt, and rotated thereby.
The first and second feeding transmission gears have a diameter equal therebetween. The second feeding transmission gear is disposed above the first feeding transmission gear, and the returning transmission gear is disposed under the first feeding transmission gear.
The arm is disposed under the sun gear and the feeding and returning planet gears, and includes a first support portion for supporting the sun gear and the returning planet gear. A second support portion supports the feeding planet gear. A rise portion has lower and upper ends, the lower end having the first support portion projecting therefrom, the upper end having the second support portion projecting therefrom, for keeping the feeding planet gear positioned higher than the returning planet gear.
The spool drive shaft is disposed in an upper wall of the cassette holder chamber. Furthermore, a transmission mechanism is extended along a vertical wall of the cassette holder chamber, for transmitting rotation of the second timing gear to the spool drive shaft.
Furthermore, a driving timing gear portion is formed with a lower face of the returning transmission gear, meshed with the timing belt, for driving the timing belt.
The photo film cassette is IX240 type.